This invention relates to improvements in signs and, more particularly, to signs carrying changeable panels, or so-called inserts.
Ubiquitous are signs of the type having slots, channels or tabs for carrying panels, or so-called inserts which are changeable to permit display of different indicia, such as price numerals, alphabetic characters, words, symbols or designs. Myriad applications call for the capability of such changeability. For example, motor fuel price signs must be capable of displaying different prices, where one or two digits of the price per gallon or liter may be subject to variation at any time.
Further, it may be desirable to change the entire character of a display. For example, if the fuel allotment for a filling station is sold out, the operation may wish to replace the inserts to change from a price display to a message such as "OUT OF GAS." Or, the operator may wish to advertise other products or services. Thus, he may wish to change the display from fuel price to "TIRE SALE," for example, by use of different inserts.
When signs of the foregoing type are used outside where exposed to various elements such as ice, rain, snow and high winds, it is important that the changeable inserts be very securely retained. Otherwise, they may become detached from the sign and be lost.
Heretofore, signs have been constructed having upset metal tabs formed in a metal base sheet, as by being struck by tooling, to engage the margin of such a sign insert. But a problem has been noted of insecure retention of the insert. Further, if the tab is required to resiliently engage the insert so that the tab will flex, the flexing ultimately may cause fatigue fracture of the tab, which then breaks off. This meets with poor commercial acceptance.